[Mesa-dev] [PATCH 2/3] radeonsi: add sampling of 4:2:2 subsampled textures

[Grigori Goronzy]

On 04.07.2014 01:24, Andy Furniss wrote:
> Maybe not 1/frame but anyway the first couple of a run have numbers
> rather than 0000s
> 
> [27977.386795] radeon 0000:01:00.0: GPU fault detected: 146 0x0c035014
> [27977.386800] radeon 0000:01:00.0:   VM_CONTEXT1_PROTECTION_FAULT_ADDR
>   0x000015E0
> [27977.386802] radeon 0000:01:00.0: VM_CONTEXT1_PROTECTION_FAULT_STATUS
> 0x03050014
> [27977.386804] VM fault (0x04, vmid 1) at page 5600, write from CB (80)
> [27977.386841] radeon 0000:01:00.0: GPU fault detected: 146 0x0c03e014
> [27977.386842] radeon 0000:01:00.0:   VM_CONTEXT1_PROTECTION_FAULT_ADDR
>   0x000015E0
> [27977.386844] radeon 0000:01:00.0: VM_CONTEXT1_PROTECTION_FAULT_STATUS
> 0x030E0014
> [27977.386846] VM fault (0x04, vmid 1) at page 5600, write from CB (224)
> 

OK, so I finally have some time to look into this.

These faults appear to be caused by the surface format mangling that vl
applies to subsampled formats, which results in an incorrect framebuffer
setup, so that rendering causes writes beyond the size of the texture
BO. Typically the only rendering operation on video buffers is clearing
them and that's why you only see these errors a couple of times after
starting a video, one for each video surface that is created. I'm not
yet sure what's the best way to solve this issue. The format mangling
would need to also change the surface width appropriately. Or maybe it's
for the best to make rendering support optional and never try to render
to subsampled surfaces. Any thoughts about this, Christian?

As for that 4:2:2 "doesn't work", AFAICT it absolutely does, but there
is no linear interpolation for chroma, so quality isn't ideal. This
seems to be a hardware restriction, unfortunately.

Grigori

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